Cystic fibrosis is a genetically transmitted disorder that affects infants, children, and young adults. Specifically, cystic fibrosis involves a dysfunction of the exocrine glands and is characterized by symptoms of chronic pulmonary disease, pancreatic deficiency, and high levels of electrolytes in the sweat of the patient. It is generally fatal, and the majority of deaths occur in victims under the age of twenty-five. One out of approximately every two thousand live births in the United States is afflicted with the disorder.
The pulmonary problems associated with cystic fibrosis result from excessive production of mucous in the respiratory tract. These problems can be treated through long term care or lung transplant and thus, early diagnosis can be beneficial in such cases. The pancreatic damage associated with the disorder can be avoided through the use of recently developed therapies, if diagnosis occurs at an early stage. It is obvious, then, that early diagnosis is crucial.
It is known that genetic testing can be used to diagnose cystic fibrosis. There are, however, a number of different genetic mutations that may result which can yield a false positive indication. Consequently, genetic testing does not presently exhibit the necessary reliability for a proper diagnosis. It happens, however, that testing the sweat of the patient provides a more reliable diagnostic result.
Two types of sweat tests are presently available. One type, a wet chemical test for the chloride ion, has the disadvantage of being labor intensive, and therefore, expensive. Further, health care insurers often will not reimburse health care providers fully for the cost of the wet chemical test. In addition, a relatively large amount of sweat is required. The other type of testing available is an electrical conductivity test which uses electrodes to directly measure the ionic concentration of salt in sweat. Currently known conductivity tests which use electrodes, however, suffer from inaccuracies caused by chemical interaction between the electrode surface and the sweat, or by contamination from previous samples. Further, like the wet chemical test, the currently known electrode tests require a relatively large amount of sweat.
A major problem with currently known testing methods is the requirement for collecting a large sample of sweat. Unfortunately, patients who are afflicted with cystic fibrosis are often sick infants or children who may not be able to produce large amounts of sweat. To help resolve this problem, perspiration is sometimes chemically induced in the patient, and the perspiration is then collected from the skin with gauze and transferred to a sample receptacle. In any case, the collection of a sufficient amount of sweat for performance of the known types of tests is very time consuming. Furthermore, a significant number of tests fail or must be repeated because of insufficient sample sizes.
In light of the above, an object of the present invention is to provide a method and apparatus for testing the conductivity of perspiration, which does not require a large amount of sweat, and which does not suffer inaccuracies resulting from chemical interaction between the sweat and electrode surfaces, or carry-over from previous samples. A further object of the present invention is to provide a method and apparatus for testing the conductivity of perspiration, which is easy and economical to use.